Large Wheels vs Pleasant Ride

I've read a number of reviews that talk about larger wheels and tires producing a less comfortable ride. I would have thought that the opposite would be true.

What do the engineering minded folks here say?

Reply to
croy
Loading thread data ...

The taller sidewall is more pliable than a narrow one. Therefore, the reasoning is that when you take off a 15 inch rim and replace it with an 18 inch rim, the resulting tire will have a sidewall that is so narrow that it will have no flexibility at all. This should translate to a harsher ride.

Reply to
Jeff Strickland

I had an 02 Highlander with 16" wheels and currently an 08 with 19" - I agree with Jeff - the larger wheels seem harsher. oh yeah the 19" cost substantially more too - it was about 1200 for 19" toyo open country when I put new ones on last year (I bought it in 08)

Reply to
ron

My opinion is that you would get a better ride with tires that have wider sidewalls. This would allow for more flexing of the side walls and provide a smoother ride.

Tire/wheel combinations with large wheels and very low profile tires (i.e., narrow sidewalls) are not consistent with providing the best ride.

Heavy tire wheel combinations are also not consistent with providing a good ride.

Ideally you want very low unsprung weight (i.e., lighter tire/wheel combinations), flexible sidewalls, a lot of spring travel, and well adjusted shock absorbers to provide a good ride. There are always compromises to be made between ride and handling. However, having a bone jarring ride is often not consistent with good handling either.

Large shiny chrome wheels with low profile tires are not the choice of the engineers trying to come up with the best ride/handling balance - they are the choice of stylist and boy racer want-to-bes. I suspect that if you want the best ride on a large car, you would go back to

15" steel wheels with 78 profile tires from around 1972. Totally uncool today. Some people think the large chrome plated mag wheels are light - they are fooling themselves in many cases.

Ed

Reply to
C. E. White

Hmmm. I was thinking along the lines of a consistant wall height, comparing cars with larger wheels *and* larger tires to cars with smaller wheels and smaller tires.

I seem to recall Consumer Reports writing that a certain make and model of SUV was generally good, but its large wheels made the ride "jittery". In the photo, I remember thinking that the tire sidewalls didn't look particularly narrow, the wheels and tires did look to be pretty good sized--something like a Murano, but I just looked again, and they didn't write that about the Murano.

Reply to
croy

Okay, I see the point.

An SUV is nothing more than a pick-up truck. The Fore Expedition is an F150, and the Excursion is an F250/350. The Yukon and Suburban are based on Chevy/GMC trucks. The Sequioa is a Toyota Tuindra and the 4Runner was at one time a Tacoma, but I'm not sure that's the case any longer.

But no matter.

The point is that SUVs with huge tires are burdened with what they refer to as UNSPRUNG Weight. This is weight that is not carried by the springs. The vehicle is carried by the springs, and anything that is touching the ground -- not part of the vehicle body -- is unsprung weight. This would include the tires and wheels, axles, brakes, the springs themselves, that sort of stuff.

You control the movement of unsprung weight with stronger springs and stiffer shocks. To the extent that the engineers find the spring rate and shock damping that works right, an SUV can have a wonderful ride or be a trip down Jittery Lane or Wallow Road.

But no matter what the vehicle, the tire diameter is a design parameter for gear ratios in the differential and transmission. One would want the correct tire diameter for the gearing selection, and if the tire diameter is changed significantly then the gear rations must be changed somewhere to keep the engine's power curve in the useful range.

If one has a passenger car or truck that is fitted with 16 inch rims and any given tire size for the vehicle in question, and they want to increase the rim diameter because they like the look of something unique, then that person must select a tire that has a narrower sidewall so keep the overall diameter of the tire the same, or face costly changes to the gear ratio or an adverse affect to performance -- assuming there are no physical limitations that come about due to the tires hitting things on the vehicle.

For every inch of increase in the rim diameter, there must be a reduction of

5% to the Aspect Ratio of the tire. The Aspect Ratio is the sidewall. If the tire specification is 205/70x16 and you wanted 17s, then your new tire size would be 205/65x17 to keep the same overall diameter. Or even larger rims would demand a 205/60x18 or 205/55x19. On these larger rims, you would likely want wider tires as well, so if you went from the 205/70x16 to a 19, your tire consideration might be 245/45x19 to keep the gearing essentially identical to what the car already has. Basically, the 16 and the 19 in my example have a functionally identical overall diameter, so the speedometer would give the same reading. and the power curve to remain in the same place.

What would happen is that the new narrow sidewall would produce a harsher ride because impacts that were formerly absorbed by the tires would be transmitted to the suspension system.

Reply to
Jeff Strickland

Not true now, and only partially ture for the original SUV type Expeditions. Expeditions have always had different rear suspension. The generation 1 Expeditions had a multi-link coil spring live axle versus the F150's live axle with leaf springs. The front suspension, while similar to the F150 of the same era used different springs, shocks, etc (plus air suspension was an option on Expeditions). Later generations of Expeditions share nothig with F150s other than the approximate track widths and engie/transmissions. Front suspension is different (although basic design is similar) and since 2003 Expeditions have had independent rear suspension. Unlike the 1st generation Expeditions, 2003 and later Expeditions don't share interior bits and front sheet metal with F150s. They are as different from F150s and current Explorers are from Rangers.

Mostly true. The Excursion always shared more of the SuperDuty components than was the case for the Expeditions and F150s. It is not to far wrong to say the Excursion was basically a long wheel base F250/350 with a cover over the bed. The front and rear suspension was basically the same except for spring and shock rates.

Based on yes, but for some time they have used completely different rear suspension (multi-link coil spring instead of leaf springs).

The Sequioa is a Toyota Tuindra

Again based on the Tundra, but with significant differences in suspension (completely different rear suspension for sure).

It has been a long time since the 4Runner was based directly on a Tacoma. The current 4Runner appears to share nothing of significance with a Tacoma beyond the drive train choices (engine / transmission / rear axle).

Ed

Reply to
C. E. White

I was making no attempt to accurately describe these vehicles. All I wanted to point out is that they are _generally_ built on truck platforms.

Reply to
Jeff Strickland

OK. I just wanted to point out that while Expeditons might be large body on frame vehicles they are clearly not an F150, particularly the second and third generation Expeditions which share little more than engines and transmissions with other large Ford Trucks. I am not even sure what you mean when you say a truck platform. To me that indicates a much higher level of commonality between the vheicles than exists between the current Ford SUVs and current Ford trucks.

Ed Ed

Reply to
C. E. White

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.